Earth cooling tubes - output

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josebcruz
Posts: 7

Earth cooling tubes - output

Postby josebcruz » Wed Aug 27, 2008 12:44 pm

Hello Support Team,

I would like to thank you the help you gave me last time.:D

I entered an idf file with the earth tube definition in DesignBuilder and it works ok.
However, I can’t see the earth tube output in DB, only in an indirect way using the cooling energy.

It’s possible to see these results in DB or I have to export the file to Energy+?

all the best

Regards,
José

Hello José,

I believe I am right in saying that earth tubes are not currently available in DesignBuilder. The best solution is likely to be to export the model as an .idf file and then use EnergyPlus to implement the Earth Tube, as EnergyPlus does have a specifically designed EarthTube model. That said, I have never tried to model that system in EnergyPlus, so cannot comment on how difficult it would be.

As an alternative, if you already know the rate at which cold air should be introduced to the space, you may be able to work around the problem by creating some form of scheduled cooling that mimics the behaviour you would expect of the earth tube.

In fact, here is a reply I just found from an earlier post on the subject:

Quote:
Hello,

You can't enter it directly in DesignBuilder by now but yo can add an earth tube definition in a text file to be included automatically in your simulation.

To do this, read InputOutpud EnergyPlus documentation then in the Simulation dialog, go to Advance tab and select your file under the idf heading.

Regards,
_________________
Laurent


So it would appear that you may be able to follow this method, which would hopefully be easier than either of the other methods I mentioned (the second of which is likely to be too inaccurate for serious use anyway).

Hopefully this helps,

All the best with your modelling work!

Regards,

Andrew Lester
AJ Lester
Posts: 158
Location: Auckland

Postby AJ Lester » Wed Aug 27, 2008 9:06 pm

Hello José,

Glad that you were able to make use of the help I offered regarding Earth Tubes. Unfortunately I haven't personally used this means of including non-standard DB equipment in the DB environment.

Hopefully a member of the E+ support team or another user with more experience than me can offer you more help.

As another suggestion that might help, you could try including a report in the text that your EarthTube is defined in. The way I imagine this working would be that this report could output the required parameters from your earth tube (i.e.

Zone, Sum, Zone EarthTube Sensible Heat Loss [J]
Zone, Sum, Zone EarthTube Sensible Heat Gain [J]
Zone, Sum, Zone EarthTube Volume [m3]
Zone, Sum, Zone EarthTube Mass [kg]
Zone, Sum, Zone EarthTube Fan Electric Consumption [J]
Zone, Average, Zone EarthTube Inlet Air Temperature [C]

could all be output report variables that might be of use)

My guess is that these parameters could then be inspected by opening the .csv file that energyplus generates and I imagine is also generated for DB by EnergyPlus.

Again, this is all just guesswork as I haven't actually done this myself, hopefully someone from DB support can confirm this or suggest an alternative.

In the meantime, all the best with your modelling work! I hope some of my guesses actually work for you!

Kind regards,

Andrew Lester
Geert Bellens
Posts: 305

Postby Geert Bellens » Sun Oct 10, 2010 2:26 pm

You can have a report in energyplus adding these lines in the idf file:

Output:Variable,
61, !- Key Value
Earth Tube Air Volume Flow Rate , !- Variable Name
hourly; !- Reporting Frequency


Where '61' is the zonenumber.
You can also use Earth Tube Zone Sensible Cooling Rate , Earth Tube Zone Sensible Heating Rate , Earth Tube Zone Inlet Air Temperature , Earth Tube Ground Interface Temperature , Earth Tube Outdoor Air Heat Transfer Rate as report variable.

But I was wondering: as you have to define the zone in the earthtube idf file, this means that only that zone benefits of the air of the earthtube ??

I would find it more logical that the air handling unit receives the total volume of air coming from the earthtube. This air is then distributed using the normal compact HVAC...Is this not possible?


Geert
ecomaterica
Posts: 7

getting earth tubes results

Postby ecomaterica » Thu Jan 13, 2011 11:56 am

Hello,

I am trying to simulate earthtubes with energy Plus. I am working with the IDF editor and once I define the earth tube i don't know how to obtain the results related to the earth tube.

Thank you.
Andy Tindale
Posts: 2669
Location: Stroud

Postby Andy Tindale » Sun Jun 01, 2014 12:13 pm

You may be interested to know that earth tubes are now included the DesignBuilder interface from v4 onwards. They can be accessed from the HVAC tab of model data.
faheemmshtaq@gmail.com
Posts: 3

Earth Tube

Postby faheemmshtaq@gmail.com » Fri Jan 29, 2016 7:14 am

Andy Tindale wrote:You may be interested to know that earth tubes are now included the DesignBuilder interface from v4 onwards. They can be accessed from the HVAC tab of model data.


I m modeling earth tube but there is no effet on total load and cooling load can u tell me the thing which I m missing I m using unitary heat cool in single family residence for 150 feet long earth tube with 15 feet depth and dai of 8 inches
xion
Posts: 3

Re: Earth cooling tubes - output

Postby xion » Wed Dec 06, 2017 6:41 pm

hi
How these 4 parameters are calculated on the earth tube?
Field: Constant Term Flow Coefficient

This number is the “A” parameter in the above earth tube equation. It is part of the user specified modifying parameters that are a function of environmental factors. This parameter, however, is a constant under all conditions and is not modified by any environmental effect. As a result, it is dimensionless.
Field: Temperature Term Flow Coefficient

This number is the “B” parameter in the above earth tube equation. It is part of the user specified modifying parameters that are a function of environmental factors. This parameter is modified by the temperature difference between the outdoor and indoor air dry-bulb temperatures. The units for this parameter are inverse Celsius.
Field: Velocity Term Flow Coefficient

This number is the “C” parameter in the above earth tube equation. It is part of the user specified modifying parameters that are a function of environmental factors. This parameter is modified by the speed of wind being experienced outside the building. The units for this parameter are s/m.
Field: Velocity Squared Term Flow Coefficient

This number is the “D” parameter in the above earth tube equation. It is part of the user specified modifying parameters that are a function of environmental factors. This parameter is modified by square of the speed of wind being experienced outside the building. The units for this parameter are s2/m2.
Luis Sousa
Posts: 370
Location: Stroud

Re: Earth cooling tubes - output

Postby Luis Sousa » Fri Dec 15, 2017 9:38 am

The best place to look for detailed information about these inputs will be on EnergyPlus Engineering Reference document. https://energyplus.net/documentation

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